This invention relates generally to electronic door locks and more particularly to locks having locking and unlocking functions driven by rotary DC motors in addition to mechanical key override.
Electrically operated door locksets are well known in the door lock industry. Typically they are "hard wired" from the standard AC system of the building through a transformer to operate a solenoid actuator in the lockset. The use of a rotary DC motor in place of a solenoid consumes less power and provides opportunities to employ the lock in battery powered "stand alone" installations. Because of the high power consumption of solenoid actuators, they are not practical for use in such installations.
Generally, in such systems, the locking function is carried out by an axially movable locking lug for simultaneously engaging slots in the outside spindle and the lock mounting hub to prevent turning of the spindle. Rotary DC motors are the preferred actuators for electronic locks; because they draw only low power. However, at stalled condition, such motors may burn out, and the electronics logic may become out of phase with the state of the lock mechanical components after a motor stall. Some presently available electronic locks employ springs between the motor drive and the locking lug to store energy from the motor during a "hang-up" condition. Such a condition may be caused, for example, by leaning on the door lever or knob while operating the lock and is ended when the leaning pressure is released. The energy may be stored between the motor drive coupling and the rotary-to-linear motion converter device, within the rotary-to-linear motion converter device, or between the rotary-to-linear motion converter device and the locking lug. In any case, this energy storage allows the motor to complete its cycle without stalling, thereby remaining in phase with the mechanical components of the lock. When the "hang-up" is released, the spring releases its energy to drive the locking lug to the required locked or unlocked condition.
Since the locking lug is held in the locking position by the spring bias, it follows that anything that can overcome the force of the spring bias, even momentarily, can be used to defeat the lock. Thus, a sharp axial blow to the outside spindle can cause the locking lug to momentarily bounce out of the hub locking slot and momentarily allow the handle to be turned to open the door.
Finally, during assembly of the locksets, the build-up of axial tolerances of components in the spindle may cause a tension or compression pre-load on the spring and thereby disturb timing between the electronic and mechanical parts of the lockset. To assure repeatable trouble free operation of the lock, such tolerance build-up must be compensated for. This requires a degree of adjustability of the components to allow for random variations of part dimensions and to complete assembly of the lock with zero load on the spring. Such adjustments are often very difficult due to limited access to set screws and other adjustment devices in an assembled lockset.
WO 95 007 33A discloses an electromechanical actuator device for causing a control member to move from a rest position to a working position and in an opposite sense to return to the rest position to a working position and in an opposite sense to return to the rest position. WO 84 03 909 discloses a lock device, including an electrically operable lock unit which can be moved between two different locations of extension and which is arranged displace able within a surrounding casing, together with a manually and key operable lock mechanism. DE 94 037 69U discloses a bolt actuating device powered by a direct current motor whose rotation is transformed into longitudinal movement by means of a gear and is transferred by means of a flexible shaft or bent lever.
The foregoing illustrates limitations known to exist in present electronic/mechanical locksets. It would, therefore, be of benefit to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.